An animal excrement disposal sheet for disposing excrement of a pet such as a cat and a dog includes as basic constituents: a liquid permeable top sheet; a liquid impermeable back sheet; and an absorbent layer that is disposed therebetween. The absorbent layer is generally composed of a water absorbent resin and a hydrophilic fiber such as pulp. Here, the water absorbent resin has higher water absorption capacity and higher water retention capacity, but lower water absorption rate than that of the hydrophilic fiber. On the other hand, the hydrophilic fiber has lower water absorption capacity but higher water absorbing rate than that of the water absorbent resin. By combining these advantages and disadvantages, the hydrophilic fiber mainly captures excrement by absorbing and diffusing in an early phase of water absorption, and then the water absorbent resin retains the excrement.
Meanwhile, it is unknown on which part of the animal excrement disposal sheet an animal will excrete. This is a major difference from an absorbent article for human use, of which the excretion position can generally be specified, and a unique problem for an animal excrement disposal sheet. Of course, a sheet that allows repeated excretions is preferable from a viewpoint of reducing effort of changing the sheet and improving cost efficiency of the sheet. However, as described above, it is unknown on which part of the sheet an animal will excrete, and due to animals not willing to excrete in a wet place, the animal tends not to excrete repeatedly on the same part of the sheet.
Accordingly, in order for a sheet to allow multiple excretions, it is required to reduce a diffusion area of excrement on a surface of the sheet after one excretion. In other words, a configuration of an absorbent layer that inhibits diffusion of excrement is a novel required performance, namely a novel problem, for an animal excrement disposal sheet.
In general, hydrophobic treatment of pulp and the like is well known as a sizing agent. However, the sizing agent is primarily used for providing water repellent characteristics to a hydrophilic fiber, and is not known to be used for mild hydrophobic treatment of a hydrophilic fiber in a water absorbent article for excrement, as an animal excrement disposal sheet.
In addition, it is known that an absorbent resin in an absorbent article that is used in contact with a wearer's body is subject to hydrophobic treatment. However, an objective of the treatment is to prevent initial gel blocking by lowering the absorption rate of the absorbent resin. In other words, it is known that liquid is diffused to a hydrophilic fiber by lowering absorption rate of the absorbent resin, but neither is known nor suggested a concept, as described above, for inhibiting diffusion of excrement to the hydrophilic fiber.